The losses in Asia tracked those in New York, where the Dow Jones industrial average fell almost 400 points, its worst decline since Sept. 22.

Global stock markets were rattled Wednesday, when Italy's borrowing costs blew past 7 percent. That was considered an important level because Greece, Portugal and Ireland required bailouts from other nations when their bond yields hit 7 percent.

While Greece has been the focus of the debt crisis for two years, Italy has recently become of greater concern because it has the third-largest economy in Europe — and because its debt, at $2.6 trillion, is too large for other European countries to absorb.

Power-sharing talks in Greece aimed at avoiding a default on its debts broke down in chaos Wednesday. Markets fear that a Greek default would lead to huge losses for European banks. That could cause a global lending freeze similar to what happened after the investment house Lehman Brothers fell in 2008.

The Dow finished down 389.24 points, at 11,780.94, its worst decline since Sept. 22. The S&P 500, the broadest major stock index, closed down 3.7 percent, or 46.82 points, at 1,229.10 — its worst day since Aug. 18. The Nasdaq composite index lost 3.9 percent at 2,621.65.

European stock markets fell sharply, too. The main stock index in Italy finished the day down 3.8 percent. The DAX index in Germany and the CAC-40 in France each declined 2.2 percent.